BOSTON—The Boston Bruins let a 3-1 series lead slip away. The Toronto Maple Leafs let a 4-1 lead in the third period of Game 7 slip away. When they went to overtime on Monday night, someone was going to have an enormous missed opportunity to dwell on for a too-long summer.

Here's hoping the weather is at least nice wherever the Maple Leafs spend their offseason.

Having scored the tying goal with 50.2 seconds left in regulation, Patrice Bergeron netted the series-winner 6:05 into overtime to give the Bruins a 5-4 victory and end the first series between the Original Six rivals since 1974. Apparently, there was a lot of pent-up drama with the 39-year wait.

The Bruins trailed by three goals after Nazem Kadri's put in the rebound of a Phil Kessel shot with 14:31 left in regulation, but Boston got goals from Nathan Horton, Milan Lucic and Bergeron to send the game to overtime.

The Bruins also played overtime in Game 7 of the first round of last year's Stanley Cup playoffs, falling to the Washington Capitals on a goal by Joel Ward. Toronto has not beaten Boston in a playoff series since 1959.

POWER UP

The Bruins were 0-for-2 on the power play, but that did not mean they were ineffective with an extra skater on the ice, not by a longshot.

Boston's two goals to tie the game in the last 1:22 of regulation came after Tuukka Rask had gone to the bench for an extra attacker. Lucic got the first, for his ninth point of the series -- one-third of his regular-season total. Then, with 50.2 seconds to go, Bergeron beat James Reimer with a long-range shot that sent TD Garden, library quiet earlier in the third period, into pandemonium.

After Rask went back between the pipes, the Bruins had a chance to win the game in regulation, but Reimer denied Brad Marchand.

THANK WHO?

Kessel's goal with 17:51 left in the third period, and his assist on Kadri's rebound goal 3:20 later gave the Maple Leafs a seemingly comfortable three-goal lead, and had Kessel on the path to a satisfying bit of crowd-silencing.

Traded from Boston to Toronto for three draft picks, most notably the first-rounder in 2010 that wound up being No. 2 overall and turned into Tyler Seguin, a rookie on the Bruins' Stanley Cup-winning team in 2011, Kessel has had to endure Boston fans chanting "Thank you, Kessel!" for Seguin's successes, even as Kessel performed at an elite level, a perennial 30-goal scorer on a mess of a team.

Nobody was chanting anything after Kessel's goal, and TD Garden was library quiet after Kadri popped in the rebound that gave Toronto a 4-1 advantage. But the Bruins still had their own noise to make.

TWO GOOD

Cody Franson picked a good time to have his first two-goal game in an NHL uniform, playing in the first Game 7 of his career.

After scoring three of his four goals this season on the power play, Franson got his first man-up goal of the series 9:35 into the game, six seconds before a high-sticking minor on Zdeno Chara was due to expire. The sequence started with a Dion Phaneuf slap shot that Rask saved, followed by a rebound try by James van Riemsdyk that Rask stuffed but could not control. The puck squirted out to the goaltender's left, and Franson swept it into the net.

Franson's second goal, at even strength, was much more stylish, as he took a pass from Clarke MacArthur and released a heavy shot from the point that Rask could not find through traffic. The goal 5:48 into the second period took the life out of the crowd, which had a nervous energy from the start, even after the Bruins took the early lead.

HE'S A KEEPER

The Bruins struck first on a goal by defenseman Matt Bartkowski, perhaps the unlikeliest of scorers, given that he had never found the back of the net in an NHL game before, coming up empty in 21 previous regular-season and playoff contests.

Bartkowski's mere presence in Boston was somewhat unexpected in itself, given that when the Bruins reportedly had a deal in place for Jarome Iginla, the 24-year-old blueliner was part of the package heading to Calgary. Iginla wound up going to the Pittsburgh Penguins instead.

The shot that Bartkowski scored on was high quality -- after taking control of the puck on a giveaway by Franson, Bartkowski waited for David Krejci and Jake Gardiner, battling for position, to get in Reimer's line of sight. Bartkowski then fired from the slot and hit the net.

D-MINUS

Already playing without injured defensemen Andrew Ference and Wade Redden, the Bruins lost Dennis Seidenberg after two shifts and 37 seconds of ice time.

Boston responded by relying even more heavily than usual on Chara. The Bruins' captain, who averaged 24:56 during the regular season, played 22:10 in the first two periods alone and finished the game with a game-high 35: 46 of icetime.